Re: [PATCH 6/7] drm/i915/guc: Kick G2H tasklet if no credits

[John Harrison <john.c.harrison@intel.com>]

On 12/11/2021 09:35, Matthew Brost wrote:
> Let's be paranoid and kick the G2H tasklet, which dequeues messages, if
> G2H credits are exhausted.
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>

> ---
>   drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> index 741be9abab68..aa6dd6415202 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> @@ -591,12 +591,19 @@ static inline bool h2g_has_room(struct intel_guc_ct *ct, u32 len_dw)
>   
>   static int has_room_nb(struct intel_guc_ct *ct, u32 h2g_dw, u32 g2h_dw)
>   {
> +	bool h2g = h2g_has_room(ct, h2g_dw);
> +	bool g2h = g2h_has_room(ct, g2h_dw);
> +
>   	lockdep_assert_held(&ct->ctbs.send.lock);
>   
> -	if (unlikely(!h2g_has_room(ct, h2g_dw) || !g2h_has_room(ct, g2h_dw))) {
> +	if (unlikely(!h2g || !g2h)) {
>   		if (ct->stall_time == KTIME_MAX)
>   			ct->stall_time = ktime_get();
>   
> +		/* Be paranoid and kick G2H tasklet to free credits */
> +		if (!g2h)
> +			tasklet_hi_schedule(&ct->receive_tasklet);
> +
>   		if (unlikely(ct_deadlocked(ct)))
>   			return -EPIPE;
>   		else